Skip to main content
Pearson+ LogoPearson+ Logo
Ch.10 - Gases
All textbooksBrown 14th EditionCh.10 - GasesProblem 120c
Previous problem
Next problem
Chapter 10, Problem 120c

An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO2 and 73.30 mL of H2O vapor expressed at STP. A separate analysis shows that the sample also contains 16.44 mg of Cl. (c) What other information would you need to know about this compound to calculate its true molecular formula?

Verified Solution

Video duration:
1m
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molecular Formula

The molecular formula of a compound indicates the actual number of each type of atom present in a molecule. It is derived from the empirical formula, which represents the simplest whole-number ratio of the elements. To determine the molecular formula, one must know the molar mass of the compound, which can be calculated from experimental data such as combustion products and elemental analysis.
Recommended video:
Guided course
02:08
Determining Molecular Formulas

Stoichiometry of Combustion

Stoichiometry involves the calculation of reactants and products in chemical reactions. In the context of combustion, it allows us to relate the volume of gases produced (like CO2 and H2O) to the amount of the original substance. By using the ideal gas law and the stoichiometric coefficients from the balanced combustion reaction, one can determine the moles of carbon and hydrogen in the sample, which are essential for finding the molecular formula.
Recommended video:
Guided course
02:24
Combustion Apparatus

Molar Mass Determination

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the true molecular formula, knowing the molar mass is crucial, as it allows for the conversion of the empirical formula to the molecular formula. This can be determined through methods such as mass spectrometry or by calculating from the combustion data and the mass of the elements present in the sample.
Recommended video:
Guided course
02:11
Molar Mass Concept
Previous problem
Next problem
Related Practice
Textbook Question

Large amounts of nitrogen gas are used in the manufacture of ammonia, principally for use in fertilizers. Suppose 120.00 kg of N21g2 is stored in a 1100.0-L metal cylinder at 280 °C. (b) By using the data in Table 10.3, calculate the pressure of the gas according to the van der Waals equation.

932
views
Textbook Question

Cyclopropane, a gas used with oxygen as a general anesthetic, is composed of 85.7% C and 14.3% H by mass. (a) If 1.56 g of cyclopropane has a volume of 1.00 L at 99.7 kPa and 50.0 °C, what is the molecular formula of cyclopropane?

1379
views
Textbook Question

An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO2 and 73.30 mL of H2O vapor expressed at STP. A separate analysis shows that the sample also contains 16.44 mg of Cl. (b) Calculate its empirical formula.

1707
views
Textbook Question

A 4.00-g sample of a mixture of CaO and BaO is placed in a 1.00-L vessel containing CO2 gas at a pressure of 97.33 kPa and a temperature of 25 °C. The CO2 reacts with the CaO and BaO, forming CaCO3 and BaCO3. When the reaction is complete, the pressure of the remaining CO2 is 20.0 kPa. (b) Calculate the mass percentage of CaO in the mixture.

1180
views
Textbook Question

Ammonia and hydrogen chloride react to form solid ammonium chloride: NH31g2 + HCl1g2¡NH4Cl1s2 Two 2.00-L flasks at 25 °C are connected by a valve, as shown in the drawing. One flask contains 5.00 g of NH31g2, and the other contains 5.00 g of HCl(g). When the valve is opened, the gases react until one is completely consumed. (a) Which gas will remain in the system after the reaction is complete?

882
views
Textbook Question

Ammonia and hydrogen chloride react to form solid ammonium chloride: NH3(g) + HCl(g) → NH4Cl(s)

Two 2.00-L flasks at 25 °C are connected by a valve, as shown in the drawing. One flask contains 5.00 g of NH3(g), and the other contains 5.00 g of HCl(g). When the valve is opened, the gases react until one is completely consumed. (b) What will be the final pressure of the system after the reaction is complete? (Neglect the volume of the ammonium chloride formed.)

4499
views